Multi-antenna wireless device with power amplifiers having different characteristics

ABSTRACT

A wireless device with power amplifiers having different characteristics to support transmission on multiple antennas is disclosed. These power amplifiers may have different gain, different maximum output power levels, etc. in order to meet requirements of different wireless systems. In an exemplary design, an apparatus includes first and second power amplifiers having different characteristics. The first power amplifier amplifies a first input signal and provides a first output signal for a first antenna. The second power amplifier amplifies the first input signal or a second input signal and provides a second output signal for a second antenna, e.g., in a MIMO mode or a transmit diversity mode. Only the first or second power amplifier amplifies another input signal and provides another output signal to the first antenna, e.g., in a CDMA mode or a GSM mode.

BACKGROUND

I. Field

The present disclosure relates generally to electronics, and more specifically to a wireless device.

II. Background

A wireless device (e.g., a cellular phone or a smart phone) may include a transmitter and a receiver coupled to an antenna to support two-way communication. For data transmission, the transmitter may modulate a radio frequency (RF) carrier signal with data to obtain a modulated signal, amplify the modulated signal to obtain an output RF signal having the proper output power level, and transmit the output RF signal via the antenna to a base station. For data reception, the receiver may obtain a received RF signal via the antenna and may condition and process the received RF signal to recover data sent by the base station.

A wireless device may include multiple transmitters and multiple receivers coupled to multiple antennas in order to improve performance. However, the circuitry to support transmission on multiple antennas typically increases the cost and size of the wireless device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless device capable of communicating with different wireless communication systems.

FIG. 2 shows a block diagram of a wireless device with a single antenna,

FIG. 3 shows a block diagram of a transmit module for a single antenna.

FIG. 4 shows a block diagram of a wireless device with two antennas.

FIG. 5 shows a block diagram of a transmit module with power amplifiers having different characteristics for two antennas.

FIGS. 6A to 6E show signal paths in the transmit module in FIG. 5 for five operating modes.

FIG. 7 shows a schematic diagram of impedance matching circuits.

FIG. 8 shows a schematic diagram of a power amplifier.

FIG. 9 shows a schematic diagram of a switch.

FIG. 10 shows a process for performing amplification by a wireless device.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description of exemplary designs of the present disclosure and is not intended to represent the only designs in which the present disclosure can be practiced. The term “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other designs. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary designs of the present disclosure. It will be apparent to those skilled in the art that the exemplary designs described herein may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the novelty of the exemplary designs presented herein.

A wireless device utilizing non-identical power amplifiers having different characteristics to support transmission on multiple antennas is described herein. Non-identical power amplifiers are power amplifiers that are designed to have different characteristics such as different gains, different maximum output power levels, different operating points, different linearity, etc. This may be achieved with different circuit designs, different transistor sizes, different bias currents, different bias voltages, etc., for the non-identical power amplifiers. The non-identical power amplifiers may be used for different radio technologies, and the different characteristics of these power amplifiers may be due to different requirements imposed by these radio technologies.

FIG. 1 shows a wireless device 110 capable of communicating with different wireless communication systems 120 and 122. Wireless systems 120 and 122 may each be a Code Division Multiple Access (CDMA) system, a Global System for Mobile Communications (GSM) system, a Long Term Evolution (LTE) system, a wireless local area network (WLAN) system, etc. A CDMA system may implement Wideband CDMA (WCDMA), cdma2000, or some other version of CDMA, which may be generically referred to as “CDMA” in the description herein. For simplicity, FIG. 1 shows wireless system 120 including one base station 130 and one system controller 140, and wireless system 122 including one base station 132 and system controller 142. In general, each wireless system may include any number of base stations and any set of network entities.

Wireless device 110 may also be referred to as a user equipment (UE), a mobile station, a terminal, an access terminal, a subscriber unit, a station, etc. Wireless device 110 may be a cellular phone, a smart phone, a tablet, a wireless modem, a personal digital assistant (PDA), a handheld device, a laptop computer, a smartbook, a netbook, a cordless phone, a wireless local loop (WLL) station, a Bluetooth device, etc. Wireless device 110 may be equipped with any number of antennas. Multiple antennas may be used to support multiple-input multiple-output (MIMO) transmission to increase throughput, transmit diversity to combat deleterious path effects (e.g., fading, multipath, and interference), carrier aggregation to increase throughput, etc. Wireless device 110 may be capable of communicating with wireless system 120 and/or 122. Wireless device 110 may also be capable of receiving signals from broadcast stations (e.g., a broadcast station 134). Wireless device 110 may also be capable of receiving signals from satellites (e.g., a satellite 150) in one or more global navigation satellite systems (GNSS).

FIG. 2 shows a block diagram of a wireless device 200, which may be an exemplary design of wireless device 110 in FIG. 1. In this exemplary design, wireless device 200 includes a data processor/controller 210, a transceiver 220, and an antenna 250. Transceiver 220 includes a transmitter 230 and a receiver 260 that support bidirectional wireless communication.

In the transmit path, data processor 210 processes (e.g., encodes and modulates) data to be transmitted and provides an analog output signal to transmitter 230. Within transmitter 230, transmit (TX) circuits 232 amplify, filter, and upconvert the analog output signal from baseband to RF and provide a modulated signal. TX circuits 232 may include amplifiers, filters, mixers, an oscillator, a local oscillator (LO) generator, a phase locked loop (PLL), etc. A power amplifier (PA) 234 receives and amplifies the modulated signal and provides an amplified RF signal having the proper output power level. Switches/duplexer 240 receive the amplified RF signal from power amplifier 234 and provide an output RF signal to antenna 250. Switches/duplexer 240 may include switches and/or a duplexer.

In the receive path, antenna 250 receives signals from base stations and/or other transmitter stations and provides a received RF signal, which is routed through switches/duplexer 240 and provided to receiver 260. Within receiver 260, a low noise amplifier (LNA) 262 amplifies the received RF signal and provides an input RF signal. Receive (RX) circuits 264 amplify, filter, and downconvert the input RF signal from RF to baseband and provide an analog input signal to data processor 210. RX circuits 264 may include amplifiers, filters, mixers, an oscillator, an LO generator, a PLL, etc.

Data processor/controller 210 may perform various functions for wireless device 200. For example, data processor 210 may perform processing for data being transmitted via transmitter 230 and received via receiver 260. Controller 210 may control the operation of TX circuits 232, power amplifier 234, RX circuits 264, LNA 262, and/or switches/duplexer 240. A memory 212 may store program codes and data for data processor/controller 210.

Wireless device 200 may support communication with CDMA, GSM, LTE, 802.11, and/or other wireless systems. Different wireless systems may utilize different radio technologies and may have different output power requirements for an output RF signal transmitted via an antenna. For example, a GSM system may require a maximum output power of +33 dBm whereas a CDMA system may require a maximum output power of +27 dBm. Wireless device 200 may be designed to provide the maximum output power for each system supported by wireless device 200.

FIG. 3 shows a block diagram of an exemplary design of a transmit module 300, which may be used for power amplifier 234 and switches/duplexer 240 in FIG. 2. Transmit module 300 includes three transmit paths 310 a, 310 b and 310 c. Transmit path 310 a includes circuits from a switch 312 a to a switch 342 a. Transmit path 310 b includes circuits from a switch 312 b to a switch 342 b. Transmit path 310 c includes circuits from a switch 312 c to a switch 342 c.

Within transmit path 310 a, switch 312 a has one end coupled to an input (RFin) of transmit module 300 and the other end coupled to the input of an input matching circuit 314 a. A driver amplifier (DA) 316 a has its input coupled to the output of matching circuit 314 a and its output coupled to the input of an inter-stage matching circuit 318 a. A first power amplifier (PA1) 320 a has its input coupled to the output of matching circuit 318 a and its output coupled to the input of an output matching circuit 322 a. A duplexer 330 has its transmit (TX) port coupled to the output of matching circuit 322 a.

Transmit path 310 b includes switch 312 b, a matching circuit 314 b, a driver amplifier 316 b, a matching circuit 318 b, a second power amplifier (PA2) 320 b, and a matching circuit 322 b, which are coupled in series as shown in FIG. 3. Transmit path 310 c includes switch 312 c, a matching circuit 314 c, a driver amplifier 316 c, and a matching circuit 318 c, which are coupled in series as shown in FIG. 3. A switch 324 has one end coupled to the output of matching circuit 318 c and the other end coupled to the TX port of duplexer 330.

Within a switchplexer 340, switch 342 a is coupled between duplexer 330 and node X. Switch 342 b is coupled between the output of matching circuit 322 b and node X. Switch 342 c is coupled between the output of matching circuit 318 c and node X. Antenna 250 is also coupled to node X. Switch 342 a, 342 b or 342 c provides an output RF signal to antenna 250. A switch (not shown in FIG. 3) may be coupled to node X and may provide a received RF signal from antenna 250 to a receiver (also not shown in FIG. 3).

In transmit path 310 a, matching circuit 314 a performs input impedance matching for driver amplifier 316 a. Driver amplifier 316 a provides amplification for an input RF signal. Matching circuit 318 a performs impedance matching between the output of driver amplifier 316 a and the input of power amplifier 320 a. Power amplifier 320 a provides amplification and high output power for the input RF signal. Matching circuit 322 a performs output impedance matching for power amplifier 320 a. The circuits in transmit path 310 b operate in similar manner as the corresponding circuits in transmit path 310 a. The circuits in transmit path 310 c operate in similar manner as the corresponding circuits in transmit path 310 a. Matching circuit 322 b performs impedance matching between the output of power amplifier 320 b and antenna 250.

Duplexer 330 supports operation in frequency division duplexing (FDD), which is utilized by many CDMA systems as well as other systems. For FDD, different frequencies are used for the downlink and uplink. Duplexer 330 can simultaneously (i) route an output RF signal from transmit path 310 a or 310 c to antenna 250 and (ii) route a received RF signal from antenna 250 to a receiver (RCVR), which is not shown in FIG. 3. Switches 342 a to 342 c support operation in time division duplexing (TDD), which is utilized by GSM systems as well as other systems. For TDD, the same frequency is used for both the downlink and uplink. Switch 342 a, 342 b or 342 c can couple an output RF signal from duplexer 330, matching circuit 322 b, or matching circuit 318 c to antenna 250 during transmit intervals. A switch (not shown in FIG. 3) can couple a received RF signal from antenna 250 to a receiver (also not shown in FIG. 3).

In the exemplary design shown in FIG. 3, transmit module 300 includes two power amplifiers 320 a and 320 b that have different characteristics and can support different wireless systems with different requirements. In particular, power amplifier 320 a may be selected to provide an output RF signal with up to +27 dBm output power in CDMA. Power amplifier 320 b may be selected to provide an output RF signal with up to +33 dBm output power in GSM. The two power amplifiers 320 a and 320 b are different and may have different gains, different maximum output power levels, different transistor sizes, different bias currents, different bias voltages, different external matching networks, etc., in order to meet the requirements of CDMA and GSM.

Either power amplifier 320 a or 320 b may be selected depending on the particular system with which a wireless device is in communication. No power amplifier may also be selected when transmit path 310 c is used for low output power.

Transmit module 300 supports a number of operating modes. Each operating mode is associated with a different signal path for an input RF signal from the input of transmit module 300 to antenna 250. One operating mode may be selected at any given moment. The signal path for the selected operating mode may be obtained by properly controlling the switches within transmit module 300. One of the switches in switchplexer 340 may be closed during a transmit interval, and one of the switches in switchplexer 340 may be closed during a receive interval. For all operating modes, a single input RF signal is applied to transmit module 300, and a single output RF signal is provided by transmit module 300. The input RF signal may be amplified by either power amplifier 320 a or 320 b, or no power amplifier.

Table 1 lists three operating modes supported by transmit module 300 and also provides the selected power amplifier, if any, and the switch settings for each operating mode. Additional operating modes may also be supported with more switches.

TABLE 1 Operating Modes for Transmit Module 300 Mode Selected Power Amplifier Switch Settings CDMA Power amplifier 320a is Switches 312a and 342a are closed; selected other switches are opened GSM Power amplifier 320b is Switches 312b and 342b are selected closed; other switches are opened Bypass Power amplifiers 320a and Switch 312c and switch 342c (or 320b are not selected switches 324 and 342a) are closed; other switches are opened

It may be desirable to support simultaneous transmission from multiple antennas by a wireless device. The multiple antennas may be used to support MIMO to achieve higher throughput, transmit diversity to improve reliably, carrier aggregation to increase throughput, and/or other transmission schemes to improve performance.

FIG. 4 shows a block diagram of a wireless device 400, which may be another exemplary design of wireless device 110 in FIG. 1. In this exemplary design, wireless device 400 includes a data processor/controller 410, two transceivers 420 a and 420 b, and two antennas 450 a and 450 b. Wireless device 400 may support CDMA, GSM, LTE, 802.11, etc.

Transceiver 420 a includes a transmitter 430 a and a receiver 460 a that support bi-directional wireless communication via antenna 450 a. Transmitter 430 a includes TX circuits 432 a and a power amplifier 434 a coupled to switches/duplexer 440 a. Receiver 460 a includes RX circuits 464 a and an LNA 462 a coupled to switches/duplexer 440 a. Similarly, transceiver 420 b includes a transmitter 430 b and a receiver 460 b that support bi-directional wireless communication via antenna 450 b. Transmitter 430 b includes TX circuits 432 b and a power amplifier 434 b coupled to switches/duplexer 440 b. Receiver 460 b includes RX circuits 464 b and an LNA 462 b coupled to switches/duplexer 440 b. The circuits in transmitters 430 a and 430 b may operate as described above for the corresponding circuits in transmitter 230 in FIG. 2. The circuits in receivers 460 a and 460 b may operate as described above for the corresponding circuits in receiver 260 in FIG. 2.

All or a portion of transceivers 420 a and 420 b may be implemented on one or more analog integrated circuits (ICs), RF ICs (RFICs), mixed-signal ICs, etc. For example, TX circuits 432 a and 432 b, power amplifiers 434 a and 434 b, LNAs 462 a and 462 b, and RX circuits 464 a and 464 b may be implemented on an RFIC. Power amplifiers 434 a and 434 b and possibly other circuits may also be implemented on a separate IC or module.

Data processor/controller 410 may perform various functions for wireless device 400. For example, data processor 410 may perform processing for data being transmitted via transmitters 430 a and 430 b and received via receivers 460 a and 460 b. Controller 410 may control the operation of TX circuits 432 a and 432 b, power amplifiers 434 a and 434 b, RX circuits 464 a and 464 a, LNAs 462 a and 462 b, and/or switches/duplexers 440 a and 440 b. A memory 412 may store program codes and data for data processor/controller 410. Memory 412 may be internal to data processor/controller 410 (as shown in FIG. 4) or external to data processor/controller 410 (not shown in FIG. 4). Data processor/controller 410 may be implemented on one or more application specific integrated circuits (ASICs) and/or other ICs.

FIG. 4 shows an exemplary design of wireless device 400 with two antennas 450 a and 450 b. In general, a wireless device may include any number of antennas, any number of transmitters, and any number of receivers. A wireless device may include (i) both a transmitter and a receiver to support data transmission and reception via a given antenna, or (ii) only a transmitter to support data transmission via the antenna, or (iii) only a receiver to support data reception via the antenna. A wireless device may also support operation on any number of frequency bands. A wireless device may include one or more transmitters and/or one or more receivers for each antenna. Each transmitter and each receiver may support operation on one or more frequency bands for a given antenna.

FIG. 5 shows a block diagram of an exemplary design of a transmit module 500, which may be used for power amplifiers 434 a and 434 b and switches/duplexers 440 a and 440 b in FIG. 4. Transmit module 500 includes four transmit paths 510 a, 510 b, 510 c and 510 d. Transmit path 510 a includes a switch 512 a, a matching circuit 514 a, a driver amplifier 516 a, a matching circuit 518 a, a first power amplifier (PA1) 520 a, and a matching circuit 522 a coupled in series, as shown in FIG. 5. Transmit path 510 b includes a switch 512 b, a matching circuit 514 b, a driver amplifier 516 b, a matching circuit 518 b, a second power amplifier (PA2) 520 b, and a matching circuit 522 b coupled in series. Transmit path 510 c includes a switch 512 c, a matching circuit 514 c, a driver amplifier 516 c, and a matching circuit 518 c coupled in series. Transmit path 510 d includes a switch 512 d, a matching circuit 514 d, a driver amplifier 516 d, and a matching circuit 518 d coupled in series. The circuits in transmit paths 510 a, 510 b, 510 c and 510 d operate as described above for the corresponding circuits in transmit paths 310 a, 310 b, 310 c and 310 c, respectively, in FIG. 3. A switch 524 is coupled between the output of matching circuit 518 c and node U. A switch 526 is coupled between the output of matching circuit 518 d and node V. A switch 528 is coupled between the output of matching circuit 522 b and node V.

Transmit module 500 further includes a duplexer 530 a and a switchplexer 540 a for antenna 450 a. Duplexer 530 a has a TX port coupled to the output of matching circuit 522 a at node U and an RX port coupled to a first receiver (RCVR1), which is not shown in FIG. 5. Within switchplexer 540 a, a switch 542 a is coupled between duplexer 530 a and node X. A switch 542 b is coupled between the output of matching circuit 522 b and node X. A switch 542 c is coupled between the output of matching circuit 518 c and node X. A switch 542 d is coupled between node U and node X. A switch (not shown in FIG. 5) may also be coupled between node X and a receiver (also not shown in FIG. 5). Antenna 450 a is coupled to node X.

Transmit module 500 further includes a duplexer 530 b and a switchplexer 540 b for antenna 450 b. Duplexer 530 b has a TX port coupled to switches 526 and 528 at node V and an RX port coupled to a second receiver (RCVR2), which is not shown in FIG. 5. Within switchplexer 540 b, a switch 544 a is coupled between node V and node Y. A switch 544 b is coupled between duplexer 530 b and node Y. A switch 544 c is coupled between the output of matching circuit 518 d and node Y. A switch (not shown in FIG. 5) may also be coupled between node Y and a receiver (also not shown in FIG. 5). Antenna 450 b is coupled to node Y.

Transmit module 500 includes two inputs, RFin1 and RFin2, that can receive one or two input RF signals at any given moment. Switches 512 a and 512 c are coupled to the RFin1 input, and switches 512 b and 512 d are coupled to the RFin2 input. A switch 512 e is coupled between the RFin1 input and the input of matching circuit 514 b. A switch may be coupled between the RFin2 input and the input of matching circuit 514 a (not shown in FIG. 5).

FIG. 5 shows an exemplary design of transmit module 500. A transmit module may also be implemented in other manners. For example, matching circuits 514 c and 518 c and driver amplifier 516 c may be omitted, and a switch may be coupled between the output (or an internal node) of matching circuit 518 a and node U. In this case, matching circuits 514 a and 518 a and driver amplifier 516 a may be reused for the bypass mode. Similarly, matching circuits 514 d and 518 d and driver amplifier 516 d may be omitted, and a switch may be coupled between the output (or an internal node) of matching circuit 518 b and node V.

Power amplifiers 520 a and 520 b may have different characteristics and performance, e.g., different gains, different maximum output power levels, different linearity, etc. This may be achieved by implementing power amplifiers 520 a and 520 b with different circuit designs, different transistor sizes, different circuit layouts, different biasing, etc., for the two power amplifiers. Power amplifiers 520 a and 520 b may be implemented on the same IC die or different IC dies.

In the exemplary design shown in FIG. 5, transmit module 500 includes all of the circuits in transmit module 300 in FIG. 3, and these circuits may operate as described above for FIG. 3. Transmit module 500 also includes a transmit path 510 d that may be used for antenna 450 b for low output power. Transmit module 500 further includes duplexer 530 b and switchplexer 540 b to support transmission via antenna 450 b. Transmit module 500 also includes switch 512 a to 512 e that can support transmission of one or two input RF signals via the two antennas 450 a and 450 b.

Transmit module 500 supports a number of operating modes. Table 2 lists five operating modes supported by transmit module 500 and also provides the selected power amplifier, if any, and the switch settings for each operating mode.

TABLE 2 Operating Modes for Transmit Module 500 Mode Selected Power Amplifier(s) Switch Settings CDMA Power amplifier 520a is selected for Switches 512a and 542a are closed; transmission via one antenna 450a other switches are opened GSM Power amplifier 520b is selected for Switches 512e and 542b are closed; transmission via one antenna 450a other switches are opened MIMO Both power amplifiers 520a and Switches 512a, 512b, 542a (or 520b are selected for transmission 542d), 528, and 544b (or 544a) are of two RF signals via two antennas closed; other switches are opened 450a and 450b Transmit Both power amplifiers 520a and Switches 512a, 512e, 542a (or Diversity 520b are selected for transmission 542d), 528, and 544b (or 544a) are of one RF signal via two antennas closed; other switches are opened 450a and 450b Bypass Power amplifiers 520a and 520b are Switches 512c, 512d, 542c (or 524 not selected; one or two RF signals and 542a), and 544c (or 526 and are transmitted via one or two 544b) are closed; other switches are antennas opened

Additional operating modes may also be supported. For example, two input signals that are phase shifted from one another may be amplified by power amplifiers 520 a and 520 b and transmitted via antennas 450 a and 450 b for transmit diversity. As another example, two input signals each carrying data on a different carrier may be amplified by power amplifiers 520 a and 520 b and transmitted via antennas 450 a and 450 b for carrier aggregation. A carrier may correspond to a range of frequencies, which may be 1.23 MHz for cdma2000, 5 MHz for WCDMA, 20 MHz for LTE, etc.

FIG. 6A shows a signal path in transmit module 500 in FIG. 5 for the CDMA mode. In the CDMA mode, a single input RF signal (e.g., a CDMA signal) is amplified by a single power amplifier 520 a and transmitted via a single antenna 450 a. The input RF signal is routed through switch 512 a and matching circuit 514 a, amplified by driver amplifier 516 a, routed through matching circuit 518 a, amplified by power amplifier 520 a, and routed through matching circuit 522 a, duplexer 530 a, and switch 542 a to antenna 450 a. Power amplifier 520 a can provide the required maximum output power (e.g., +27 dBm) for CDMA.

FIG. 6B shows a signal path in transmit module 500 for the GSM mode. In the GSM mode, a single input RF signal (e.g., a GSM signal) is amplified by a single power amplifier 520 b and transmitted via a single antenna 450 a. The input RF signal is routed through switch 512 e and matching circuit 514 b, amplified by driver amplifier 516 b, routed through matching circuit 518 b, amplified by power amplifier 520 b, and routed through matching circuit 522 b and switch 542 b to antenna 450 a. Power amplifier 520 b can provide the required maximum output power (e.g., +33 dBm) for GSM.

FIG. 6C shows signal paths in transmit module 500 for the MIMO mode. In the MIMO mode, two input RF signals are amplified by two power amplifiers 520 a and 520 b and transmitted via two antennas 450 a and 450 b. A first input RF signal is routed through switch 512 a and matching circuit 514 a, amplified by driver amplifier 516 a, routed through matching circuit 518 a, amplified by power amplifier 520 a, and routed through matching circuit 522 a. The first input RF signal may further be routed (i) through switch 542 d to antenna 450 a for TDD (as shown in FIG. 6C) or (ii) through duplexer 530 a and switch 542 a to antenna 450 a for FDD (not shown in FIG. 6C). A second input RF signal is routed through switch 512 b and matching circuit 514 b, amplified by driver amplifier 516 b, routed through matching circuit 518 b, amplified by power amplifier 520 b, and routed through matching circuit 522 b and switch 528. The second input RF signal may further be routed (i) through switch 544 a to antenna 450 b for TDD (as shown in FIG. 6C) or (ii) through duplexer 530 b and switch 544 b to antenna 450 b for FDD (not shown in FIG. 6C). Power amplifiers 520 a and 520 b can provide the required maximum output power for the two output RF signals transmitted via antennas 450 a and 450 b for MIMO.

FIG. 6D shows signal paths in transmit module 500 for the transmit diversity mode. In the transmit diversity mode, a single input RF signal is amplified by two power amplifiers 520 a and 520 b and transmitted via two antennas 450 a and 450 b. The input RF signal is routed through switch 512 a and matching circuit 514 a, amplified by driver amplifier 516 a, routed through matching circuit 518 a, amplified by power amplifier 520 a, and routed through matching circuit 522 a, and either switch 542 d (as shown in FIG. 6D) or duplexer 530 a and switch 542 a (not shown in FIG. 6D) to antenna 450 a. The input RF signal is also routed through switch 512 e and matching circuit 514 b, amplified by driver amplifier 516 b, routed through matching circuit 518 b, amplified by power amplifier 520 b, and routed through matching circuit 522 b, switch 528, and either switch 544 a (as shown in FIG. 6D) or duplexer 530 b and switch 542 b (not shown in FIG. 6D) to antenna 450 b. Power amplifiers 520 a and 520 b can provide the required maximum output power for the two output RF signals transmitted via antennas 450 a and 450 b for transmit diversity.

FIG. 6E shows signal paths in transmit module 500 for the bypass mode. In the bypass mode, one or more input RF signals are amplified by one or more driver amplifiers and transmitted via one or more antennas. A first input RF signal is routed through switch 512 c and matching circuit 514 c, amplified by driver amplifier 516 c, and routed through matching circuit 518 c and switch 542 c (or switch 524, duplexer 530 a, and switch 542 a) to antenna 450 a. The first input RF signal or a second input RF signal is routed through switch 512 d and matching circuit 514 d, amplified by driver amplifier 516 d, and routed through matching circuit 518 d and switch 544 c (or switch 526, duplexer 530 b, and switch 544 b) to antenna 450 b. Driver amplifiers 516 c and 516 d can provide the desired output power for the output RF signals transmitted via antennas 450 a and 450 b in the bypass mode.

As shown in FIGS. 3 and 5, few additional circuitry may be used to support MIMO, transmit diversity, and carrier aggregation modes for two antennas as well as the CDMA, GSM and bypass modes already supported by a wireless device. In particular, MIMO and carrier aggregation may be supported with additional switches so that (i) two input signals can be applied to two power amplifiers and (ii) two output signals from the two power amplifiers can be provided to two antennas, as shown in FIG. 6C. Transmit diversity may be supported with additional switches so that (i) a single input signal can be applied to two power amplifiers and (ii) two output signals from the two power amplifiers can be provided to two antennas, as shown in FIG. 6D. The additional switches allow existing power amplifiers to be reused for MIMO, transmit diversity, and/or carrier aggregation, which results in little additional cost to support these modes. The ability to efficiently support MIMO, transmit diversity, and/or carrier aggregation may be especially desirable to increase uplink throughput to support video-centric activities (e.g., Skype calls), femto-cell, and Mi-fi applications.

FIG. 7 shows a schematic diagram of exemplary designs of the matching circuits within transmit module 500 in FIG. 5. For clarity, only circuits in transmit path 510 a are shown in FIG. 7. Within matching circuit 514 a, a capacitor 712 has one end coupled to switch 512 a and the other end coupled to node E. An inductor 714 is coupled between node E and the input of driver amplifier 516 a. A capacitor 716 is coupled between node E and circuit ground. A resistor 718 is coupled between the input of driver amplifier 516 a and a bias voltage.

Within matching circuit 518 a, an inductor 722 is coupled between the output of driver amplifier 516 a and a power supply. A capacitor 724 is coupled between the output of driver amplifier 516 a and node F. A capacitor 726 is coupled between node F and circuit ground. An inductor 728 is coupled between node F and the input of power amplifier 520 a. A resistor 730 is coupled between the input of power amplifier 520 a and a bias voltage.

Within matching circuit 522 a, an inductor 732 is coupled between the input and output of matching circuit 522 a. An inductor 734 is coupled between the input of matching circuit 522 a and the power supply. A capacitor 736 is coupled between output of matching circuit 522 a and circuit ground.

FIG. 7 shows exemplary designs of matching circuits 514 a, 518 a and 522 a. In general, a matching circuit may be implemented with any topology such as a lowpass network, a highpass network, a bandpass network, etc. A matching circuit may also be implemented with any number of reactive elements (e.g., inductors and capacitors) to obtain the desired performance. The reactive elements may have values selected based on the impedances at the input and output of the matching circuit. A matching circuit may also be implemented with one or more tunable reactive elements (e.g., one or more variable capacitors or varactors) to enable tuning of impedance matching. Tunable reactive elements may enable better impedance matching for different loads coupled to the matching circuit and/or different frequencies. For example, tunable reactive elements may enable matching circuit 522 a to match to either duplexer 530 a or antenna 450 a in FIG. 5 and/or to match to antenna 450 a at different frequencies.

Power amplifiers 520 a and 520 b in FIG. 5 may be implemented with various circuit designs. Each power amplifier may be implemented to obtain the desired characteristics and performance for that power amplifier.

FIG. 8 shows a schematic diagram of an exemplary design of a power amplifier 800, which may be used for power amplifier 520 a or 520 b in FIG. 5. Power amplifier 800 includes K N-channel metal oxide semiconductor (NMOS) transistors 810 a through 810 k coupled in a stack, where K may be any integer value. The bottommost NMOS transistor 810 a has its source coupled to circuit ground and its gate receiving an input signal (PAin) via an AC coupling capacitor 822. Each higher up NMOS transistor 810 in the stack has its source coupled to the drain of another NMOS transistor below in the stack. The topmost NMOS transistor 810 k has its drain providing an output signal (PAout). A load inductor 812 is coupled between a power supply (Vdd) and the drain of the topmost NMOS transistor 810 k and provides DC bias current for power amplifier 800. Load inductor 812 may be part of a matching circuit that is coupled to the output of power amplifier 800. The gates of NMOS transistor 810 a through 810 k receive K bias voltages, Vbias1 through VbiasK, via K resistors 820 a through 820 k, respectively. The bias voltages may be generated to turn on power amplifier 800 when it is enabled and to turn off power amplifier 800 when it is disabled.

The PAout signal may have a large voltage swing, which may exceed a breakdown voltage of each NMOS transistor 810. The large voltage swing of the PAout signal may be split or distributed approximately equally across the K NMOS transistors 810 a through 810 k. Each NMOS transistor 810 may then observe only a fraction of the voltage swing, which may be less than the breakdown voltage of each NMOS transistor in order to achieve high reliability. The K bias voltages Vbias1 through VbiasK may be selected to provide the desired voltage splitting of the PAout signal, e.g., so that each NMOS transistor observes approximately 1/K-th of the voltage swing.

FIG. 8 shows an exemplary design of a power amplifier, which may also be implemented in other manners. For example, a power amplifier may be implemented with transistors of other types, or other circuit topologies, etc. The exemplary design shown in FIG. 8 may also be used for any one of the driver amplifiers in FIG. 5. Power amplifiers 520 a and 520 b (and also driver amplifiers) may have different requirements for input power, output power, linearity, harmonics, etc. Power amplifiers 520 a and 520 b (and also driver amplifiers) may thus have different numbers of stacked NMOS transistors, different transistor sizes, different load inductors, different bias voltages, different bias currents, different impedance matching circuits, and/or different characteristics for other parameters.

FIG. 9 shows a schematic diagram of a switch 900, which may be used for any one of the switches in FIG. 5. Within switch 900, M NMOS transistors 910 a through 910 m are coupled in a stacked, where M may be any integer value. Each NMOS transistor 910 (except for the bottommost NMOS transistor 910 a) has its source coupled to the drain of the next NMOS transistor in the stack. The topmost NMOS transistor 910 m has its drain receiving an input signal (Vin), and the bottommost NMOS transistor 910 a has its source providing an output signal (Vout). Each NMOS transistor 910 may be implemented with a symmetric structure, and the source and drain of each NMOS transistor may be interchangeable. M resistors 920 a through 920 m have one end coupled to node A and the other end coupled to the gates of NMOS transistors 910 a through 910 m, respectively. A control signal (Vctrl) is provided to node A. The control signal may be set to a high voltage to turn on switch 900 or to a low voltage to turn off switch 900.

Resistors 920 a through 920 m may have relatively large resistance, e.g., in the kilo Ohms range. When NMOS transistors 910 are turned on, resistors 920 may reduce signal loss by presenting a large resistance to the Vin signal in the leakage path through the gate-to-source and gate-to-drain capacitances of each NMOS transistor. When NMOS transistors 910 are turned off, resistors 920 may help to distribute the voltage swing of the Vin signal approximately evenly across the M NMOS transistors 910 in the stack. NMOS transistors 910 may be designed with a sufficiently large size in order to reduce the on resistance when switch 900 is turned on.

Although not shown in FIG. 9, M resistors may be coupled between the drain and source of NMOS transistors 910 a through 910 m, one resistor for each NMOS transistor 910. These resistors may maintain the sources of NMOS transistors 910 b through 910 m at approximately the same voltage when switch 900 is in the off state. This may then result in matching bias conditions for all M NMOS transistors 910 a through 910 m, which may result in equal voltage splitting during the off state.

FIG. 9 shows an exemplary design of a switch, which may also be implemented in other manners. For example, a switch may be implemented with transistors of other types, or with other circuit topologies, etc. A switch may also be implemented with micro-electro-mechanical system (MEMS), silicon-on-insulator (SOI), or some other semiconductor process technology.

In an exemplary design, an apparatus (e.g., a wireless device, an IC, a circuit module, etc.) may comprise first and second power amplifiers. The first power amplifier (e.g., power amplifier 520 a in FIG. 5) may amplify a first input signal and provide a first output signal for a first antenna (e.g., antenna 450 a) in a first operating mode. The second power amplifier (e.g., power amplifier 520 b) may amplify the first input signal or a second input signal and provide a second output signal for a second antenna (e.g., antenna 450 b) in the first operating mode. The first and second power amplifiers may have different characteristics, e.g., different gains, different maximum output power levels, different circuit designs, different transistor sizes, different bias voltages, different bias currents, etc.

In an exemplary design, the first and second power amplifiers may amplify the first and second input signals (i.e., different input signals) and provide the first and second output signals for the first and second antennas for MIMO transmission in the first operating mode (e.g., as shown in FIG. 6C). In another exemplary design, the first and second power amplifiers may both amplify the first input signal (i.e., the same input signal) and provide the first and second output signals for the first and second antennas for transmit diversity in the first operating mode (e.g., as shown in FIG. 6D). In yet another exemplary design, the first power amplifier may amplify the first input signal for a first carrier and the second power amplifier may amplify the second input signal for a second carrier for carrier aggregation in the first operating mode.

In an exemplary design, the first power amplifier may amplify a third input signal (e.g., a CDMA signal) and provide a third output signal for the first antenna in a second operating mode (e.g., as shown in FIG. 6A). The second power amplifier may amplify a fourth input signal (e.g., a GSM signal) and provide a fourth output signal for the first antenna in a third operating mode (e.g., as shown in FIG. 6B). The second power amplifier may be disabled in the second operating mode, and the first power amplifier may be disabled in the third operating mode. In an exemplary design, the second and third operating modes may be associated with different radio technologies (e.g., CDMA and GSM), and the fourth output signal may have a higher maximum output power than the third output signal.

In an exemplary design, a driver amplifier (e.g., driver amplifier 516 c in FIG. 5) may amplify an input signal and provide an output signal for the first antenna in a fourth operating mode (e.g., a bypass mode, as shown in FIG. 6E). This input signal is not amplified by any power amplifier in the fourth operating mode.

In an exemplary design, a first driver amplifier (e.g., driver amplifier 516 a in FIG. 5) may amplify the first input signal in the first operating mode. A first matching circuit (e.g., matching circuit 518 a) may be coupled between the first driver amplifier and the first power amplifier. A second driver amplifier (e.g., driver amplifier 516 b) may amplify the first or second input signal in the first operating mode. A second matching circuit (e.g., matching circuit 518 b) may be coupled between the second driver amplifier and the second power amplifier. In an exemplary design, a third matching circuit (e.g., matching circuit 522 a) may be coupled to the output of the first power amplifier. A fourth matching circuit (e.g., matching circuit 522 b) may be coupled to the output of the second power amplifier.

In an exemplary design, a first duplexer (e.g., duplexer 530 a) may be coupled between the first power amplifier and the first antenna. A second duplexer (e.g., duplexer 530 b) may be coupled between the second power amplifier and the second antenna.

In an exemplary design, a first switch (e.g., switch 512 a) may route the first input signal toward the first power amplifier in the first operating mode when the first switch is enabled. A second switch (e.g., switch 512 e) may route the first input signal toward the second power amplifier in the first operating mode when the second switch is enabled. A third switch (e.g., switch 512 b) may route the second input signal toward the second power amplifier in the first operating mode when the third switch is enabled. In an exemplary design, a fourth switch (e.g., switch 542 a or 542 d) may route the first output signal from the first power amplifier toward the first antenna in the first operating mode. A fifth switch (e.g., switch 544 a or 544 b) may route the second output signal from the second power amplifier toward the second antenna in the first operating mode.

In an exemplary design, the first and second power amplifiers may be fabricated on a single IC. In another exemplary design, the first and second power amplifiers may be fabricated on two separate ICs.

FIG. 10 shows an exemplary design of a process 1000 for performing amplification by a wireless device. A first input signal may be amplified with a first power amplifier to obtain a first output signal for a first antenna in a first operating mode (block 1012). The first input signal or a second input signal may be amplified with a second power amplifier to obtain a second output signal for a second antenna in the first operating mode (block 1014). The first and second power amplifiers may have different characteristics.

In an exemplary design, the first and second input signals (i.e., different input signals) may be amplified with the first and second power amplifiers to obtain the first and second output signals for the first and second antennas for MIMO transmission in the first operating mode. In another exemplary design, the first input signal (i.e., the same input signal) may be amplified with both the first and second power amplifiers to obtain the first and second output signals for the first and second antennas for transmit diversity in the first operating mode. In yet another exemplary design, the first input signal for a first carrier may be amplified with the first power amplifier and the second input signal for a second carrier may be amplified with the second power amplifier to obtain the first and second output signals for the first and second antennas for carrier aggregation in the first operating mode.

In an exemplary design, a third input signal (e.g., a CDMA signal) may be amplified with the first power amplifier to obtain a third output signal for the first antenna in a second operating mode (block 1016). A fourth input signal (e.g., a GSM signal) may be amplified with the second power amplifier to obtain a fourth output signal for the first antenna in a third operating mode (block 1018). The second power amplifier may be disabled in the second operating mode, and the first power amplifier may be disabled in the third operating mode.

Power amplifiers having different characteristics and supporting transmission on multiple antennas, as described herein, may be implemented on an IC, an analog IC, an RFIC, a mixed-signal IC, an ASIC, a printed circuit board (PCB), an electronic device, etc. The power amplifiers may also be fabricated with various IC process technologies such as complementary metal oxide semiconductor (CMOS), NMOS, P-channel MOS (PMOS), bipolar junction transistor (BJT), bipolar-CMOS (BiCMOS), silicon germanium (SiGe), gallium arsenide (GaAs), heterojunction bipolar transistors (HBTs), high electron mobility transistors (HEMTs), silicon-on-insulator (SOI), etc.

An apparatus implementing the power amplifiers having different characteristics described herein may be a stand-alone device or may be part of a larger device. A device may be (i) a stand-alone IC, (ii) a set of one or more ICs that may include memory ICs for storing data and/or instructions, (iii) an RFIC such as an RF receiver (RFR) or an RF transmitter/receiver (RTR), (iv) an ASIC such as a mobile station modem (MSM), (v) a module that may be embedded within other devices, (vi) a receiver, cellular phone, wireless device, handset, or mobile unit, (vii) etc.

In one or more exemplary designs, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. 

What is claimed is:
 1. An apparatus comprising: a first power amplifier configured to amplify a first input signal and provide a first output signal for a first antenna; and a second power amplifier configured to amplify the first input signal or a second input signal and provide a second output signal for a second antenna, the first and second power amplifiers having different characteristics.
 2. The apparatus of claim 1, wherein the first and second power amplifiers have at least one of a different gains, different maximum output power levels, different circuit designs, different transistor sizes, different bias voltages, and different bias currents.
 3. The apparatus of claim 1, wherein the first and second power amplifiers are configured to amplify the first and second input signals and provide the first and second output signals for the first and second antennas for multiple-input multiple-output (MIMO) transmission.
 4. The apparatus of claim 1, wherein the first and second power amplifiers are both configured to amplify the first input signal and provide the first and second output signals for the first and second antennas for transmit diversity.
 5. The apparatus of claim 1, wherein the first power amplifier is configured to amplify the first input signal for a first carrier and the second power amplifier is configured to amplify the second input signal for a second carrier for carrier aggregation.
 6. The apparatus of claim 1, wherein the first and second power amplifiers are configured to concurrently provide the first and second output signals for the first and second antennas in a first operating mode, wherein only the first power amplifier is configured to amplify a third input signal and provide a third output signal for the first antenna in a second operating mode, and wherein only the second power amplifier is configured to amplify a fourth input signal and provide a fourth output signal for the first antenna in a third operating mode.
 7. The apparatus of claim 6, wherein the second power amplifier is disabled in the second operating mode and the first power amplifier is disabled in the third operating mode.
 8. The apparatus of claim 6, wherein the second and third operating modes are associated with different radio technologies, and wherein the fourth output signal has a higher maximum output power than the third output signal.
 9. The apparatus of claim 6, further comprising: a driver amplifier configured to amplify a fifth input signal and provide a fifth output signal for the first antenna in a fourth operating mode, the fifth input signal is not amplified by any power amplifier in the fourth operating mode.
 10. The apparatus of claim 1, further comprising: a first driver amplifier configured to amplify the first input signal; a first matching circuit coupled between the first driver amplifier and the first power amplifier; a second driver amplifier configured to amplify the first or second input signal; and a second matching circuit coupled between the second driver amplifier and the second power amplifier.
 11. The apparatus of claim 1, further comprising: a first switch configured to route the first input signal toward the first power amplifier when the first switch is enabled; a second switch configured to route the first input signal toward the second power amplifier when the second switch is enabled; and a third switch configured to route the second input signal toward the second power amplifier when the third switch is enabled.
 12. The apparatus of claim 1, further comprising: a first switch configured to route the first output signal from the first power amplifier toward the first antenna when the first switch is enabled; and a second switch configured to route the second output signal toward the second antenna when the second switch is enabled.
 13. The apparatus of claim 1, wherein the first and second power amplifiers are fabricated on a single integrated circuit (IC).
 14. A method comprising: amplifying a first input signal with a first power amplifier to obtain a first output signal for a first antenna; and amplifying the first input signal or a second input signal with a second power amplifier to obtain a second output signal for a second antenna, the first and second power amplifiers having different characteristics.
 15. The method of claim 14, wherein the amplifying the first input signal or the second input signal with the second power amplifier comprises amplifying the second input signal with the second power amplifier to obtain the second output signal for the second antenna, the first and second output signals being transmitted via the first and second antennas for multiple-input multiple-output (MIMO) transmission.
 16. The method of claim 14, wherein the amplifying the first input signal or the second input signal with the second power amplifier comprises amplifying the first input signal with the second power amplifier to obtain the second output signal for the second antenna, the first and second output signals being transmitted via the first and second antennas for transmit diversity.
 17. The method of claim 14, wherein the amplifying the first input signal with the first power amplifier comprises amplifying the first input signal for a first carrier with the first power amplifier, and wherein the amplifying the first input signal or the second input signal with the second power amplifier comprises amplifying the second input signal for a second carrier with the second power amplifier to obtain the second output signal for the second antenna, the first and second output signals being transmitted via the first and second antennas for carrier aggregation.
 18. The method of claim 14, wherein the first and second power amplifiers are configured to concurrently provide the first and second output signals for the first and second antennas in a first operating mode, the method further comprising: amplifying a third input signal with the first power amplifier to obtain a third output signal for the first antenna in a second operating mode; disabling the second power amplifier in the second operating mode; amplifying a fourth input signal with the second power amplifier to obtain a fourth output signal for the first antenna in a third operating mode; and disabling the first power amplifier in the third operating mode.
 19. An apparatus comprising: first means for amplifying configured to amplify a first input signal and provide a first output signal for a first antenna; and second means for amplifying configured to amplify the first input signal or a second input signal and provide a second output signal for a second antenna, the first means for amplifying and the second means for amplifying having different characteristics.
 20. The apparatus of claim 19, wherein the second means for amplifying is configured to amplify the second input signal and provide the second output signal for the second antenna, the first and second output signals being transmitted via the first and second antennas for multiple-input multiple-output (MIMO) transmission.
 21. The apparatus of claim 19, wherein the second means for amplifying is configured to amplify the first input signal and provide the second output signal for the second antenna, the first and second output signals being transmitted via the first and second antennas for transmit diversity.
 22. The apparatus of claim 19, wherein the first means for amplifying is configured to amplify the first input signal for a first carrier and provide the first output signal for the first antenna, and wherein the second means for amplifying is configured to amplify the second input signal for a second carrier and provide the second output signal for the second antenna, the first and second output signals being transmitted via the first and second antennas for carrier aggregation. 